Health Data security, characterized in terms of data privacy, authenticity, and integrity, is a vital issue when digital images and other patient information are transmitted through public networks in teleradiology and other telehealth applications. Mandates for ensuring health data security have been issued by the federal government (e.g. HIPAA [Health Insurance Portability and Accountability Act]), and guidelines such as DICOM (Digital Imaging and Communication in Medicine) standard continue to be published by organizing bodies in healthcare (e.g. American College of Radiology); however, there has not been a systematic research and development effort within the medical imaging community to address this critical matter. Over the past six years, members in the Image Processing and Informatics Laboratory/Children's Hospital Los Angeles/University of Southern California (PI/CHLA/USC) has actively researched image security issues related to PACS (Picture Archiving and Communication System) and telehealth with very encouraging results. This application represents an organized and rigorous approach to further research on this topic based on this experience. The proposal outlines the systematic development of the digital envelope (DE) concept to assure data integrity, authenticity, and privacy during image/data transmission through public networks. The DE includes the digital signature (DS) of the image as well as encrypted patient information from the DICOM image header. The proposal delineates eight specific tasks, including review and selection of digital security technologies suitable for medical imaging applications, revamping our existing DE security algorithm based on these new selections, designing the DE to be DICOM compliant, and performing a three-phase evaluation from the laboratory, to intra-hospital, and finally inter-hospital environments. The three-year research plan will culminate in the delivery of a portable, self-contained, and evolving DE package available for the medical image community to use in telemedicine and teleradiology applications. For telemedicine and teleradiology, since data cannot be limited within a private local area network protected by a firewall, the DE package offers the most useful security assurance. This method also provides additional image/data assurance to conventional network security protections.